Alicorns exhibit the traits of all three tribes, and we've seen the ascension of two new alicorns in the series so far.

Twilight was a unicorn who became an alicorn through her understanding of her element of friendship.
Cadence was a pegasus who became an alicorn through her understanding of love.
All that's needed now for the full set of magical and tribal origins of neoalicorns is an earth pony.

I dunno whether whoever Voice of God has passed to cares to complete the set, though_________________butts

mares can reproduce with mares and stallions can reproduce with stallions, as well as the expected mare+stallion reproduction

don't ask how, cuz I haven't thought this through
magic or summat

also bi is "straight" in Equestria and hetero and homo are both "bent"

Word of Faust says they reproduce sexually (even if they do, that doesn't necessarily preclude both genders having... er, both sets of...), but there is no evidence of them having any sort of genitalia in the show, and if we were still following Word of Faust there would only be two alicorns.
Checkmate, atheists!

k? k._________________butts

Last edited by Heretical Rants on Wed Sep 25, 2013 4:41 am; edited 9 times in total

but budding is super creepy with anything that has a skeleton, and it doesn't explain the huge amount of variety seen between individuals in the population and between generations, nor the fact that everypony has two parents_________________butts

There are actually five known tribes of ponies: the well-known three(earth ponies, pegasi, unicorns), plus bat ponies and crystal ponies.
Alicorns exhibit the traits of the main three tribes plus something more specialized.

Larsen and Faust are on record for saying that the bat ponies seen in Luna's guard are actually distinct from the pegasi and come from faraway caves.

Nightmare Moon's wings, with their pointed tips, look like something of a blend between the bat ponies' wings and the usual feathered wings, and her eyes have the same slits for pupils. Luna herself is probably a very important figure for the bat ponies and she may naturally exhibit some of their traits in more subtle ways.

It isn't entirely clear whether the crystal ponies are a distinct tribe, or if they're just earth ponies that have been influenced by ambient magic, but Princess (or is it Empress, now?) Cadence has a well-established affiliation with the Crystal Empire and even has an important crystal artifact as part of her cutie mark

this just begs the questions, then
is there any specific minor tribe for which Celestia is responsible? Will Twilight find she has a similar affiliation?_________________butts